The present invention relates to an ultrasonic driving device comprising a stator using a ring type piezoelectric vibrator or vibrators and metal blocks.
In a known ultrasonic motor using a piezoelectric vibrator, two groups of electrodes are attached to one side of a ring type piezoelectric ceramic, the two groups of electrodes are so positioned that standing waves respectively generated by the two groups of electrodes are shifted every .pi./2 in each position. The parts of the ring type piezoelectric vibrator corresponding to the electrode are alternately polarized in reverse. Also, the two groups of the electrodes are respectively connected to two oscillators for respectively generating alternating currents having .pi./2 phase shift each other. When the alternating currents from the two oscillators are respectively applied to the two groups of electrodes, the two standing waves having a .pi./2 phase shift to each other generated on the surfaces of the ring type piezoelectric vibrator and then progressive waves owing to a compound of the two standing waves generate on the surfaces of the ring type piezoelectric vibrator. Therefore, when a rotary member is put on the ring type piezoelectric vibrator and the rotary member is strongly pressed to the ring type piezoelectric vibrator, the rotary member is rotated by the progressive waves.
In the prior ultrasonic motor, since the ring type piezoelectric vibrator must be polarized in many portions thereof and the two oscillators must be connected to the electrodes, the composition of the ring type piezoelectric vibrator is complex and the cost of the ultrasonic motor becomes expensive.
There is known an ultrasonic motor comprising a Langevin type vibrator having two ring type piezoelectric vibrators put between two metal blocks. In this ultrasonic motor, a twisting joint body is connected to the end of the one metal block by a bolt for fixing the metal blocks and the piezoelectric vibrators and a rotary member is pressed on the twisting joint body by a spring.
However, the composition of the ultrasonic motor is complex and its cost becomes expensive.